I hope you are asking two separate unrelated questions, because there's no point in doing cost segregation for properties held inside your self-directed solo 401k, save for some very rare exceptions.Some of the Bigger Pockets experts who operate reputable costs segregation companies are @Bernard Reisz, @Yonah Weiss and @Julio GonzalezSome of the Bigger Pockets experts who offer Solo 401k administrator services are @Dmitriy Fomichenko, again @Bernard Reisz and @Brian EastmanReach out to them and see if they can help.

They either had below mkt. rents or high vacancies and bad reputations and with super managing them I significantly grew the cash flow. 

You can look at a mobile home and see it as an easy rental with new carpet, trim and some paint but there are other bigger uglier expenses that can come up.Roof Replacement, soft floors (water damage) in kitchens and bathrooms- most floors are particle board, exterior door replacement (special order), underbelly insulation falling, bad hot water tanks with rotten floor underneath (real joy), bad windows (water again), bad bloated siding (water), water damaged base frame around perimeter of home, cracked tubs (special orders) and frozen pipes (Good luck finding a plumber to come work on a mobile home- they do not exist). 

I would appreciate any advice on whether it's a good idea to invest in land on a slope and the potential challenges of building on such terrain.If this seems like a worthwhile investment, can anyone recommend reputable construction companies that specialize in cabin builds on slopes? 

You should bill them both for the damages, take pictures and go to court.

With that said can anyone suggest reputable lenders that are able to assist me with a debt consolidation loan of ~25K?  

Higher rent, guaranteed rent payment, collections and damage you just call their commanding officer.  

I know it can depend on factors like the borrower’s credit, payment history, and loan terms, but I’m looking for general guidance or ballpark percentages based on your experience.Top Buyers/Companies:Who do you recommend as reputable buyers for these types of notes?

@Saul Clavijo make sure you understand you will be getting into Class C properties at those numbers.Food for though below, DM us to chat more about Detroit:--------------------------------------------------------------------------------------------------------Recommend you first figure out the property Class you want to invest in, THEN figure out the corresponding location to invest in.Property Class will typically dictate the Class of tenant you get, which greatly IMPACTS rental income stability and property maintenance/damage by tenants.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.If you buy/renovate a property in Class D area to Class A standards, what quality of tenant will you get?

If they damage your property here, you're SOL!